A 4.8-magnitude aftershock has been widely felt across Canterbury this afternoon.

GeoNet volcanologist Brad Scott said the shake at 4.17pm was 8km deep and centred near Diamond Harbour, southeast of Christchurch.

"It is at the bigger end of the expected aftershocks at this time. It's been quiet widely felt across Canterbury," he said.

"The last couple of days have been relatively quiet. There has been nothing significant for the last 16 to 18 hours."

Katie Washington was standing in a Riccarton supermarket when the quake hit.

''It was long and felt big. The shelves started to sway a bit. Scary.

Nickie Barlow, who lives in Taylors Mistake, said it began with a rumble and built up to "a real puncher".  

''A few things fell off shelves, nothing big though. My neighbour was on his way over the hill and reported a cloud of dust at Whitewash Head.''

Woolston resident Patrick Lewis said his four-year-old child started crying and photos fell off  the table.

''It was a good shake. The biggest we have felt for a while. Let's hope its not a start off things to come."

Cashmere resident Lisa Dixon said it was the "strongest and longest shock in a long while".